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Discussion Starter · #1 ·
'70 CB450 All stock with new Chinese points. I have filed out the mounting holes to be able to time and shimmed the slop out of them with sanded down washers.

I have timed it, and for all intents and purposes it's dead on. But I will check again this evening. (I like getting sprayed with oil)
The advance does not kick in till ~4500 - 5000 rpms and it's abrupt. It does not slowly climb with the rpms it just goes to full advance in the span of a couple of hundred rpms.
While riding it, around 5500 to 6000 rpms it loses power and by 6500 there is no more and its spitting and sputtering.
No sign of carb problems. All clamps around air related things like intake manifolds and air cleaners are tight and I doubt very much if there is an air leak. Idles fine and revs up and comes down (no hanging). No leaks, no blockages in the fuel lines, gas flows fine.
The right side cylinder (as you sit on the bike) seems to spit and backfire more than the left. Has just a tinge of smoke too.
Have not run a compression test yet - but both cylinders feel better than my CB650 with a head gasket leak and that runs better the higher you get into the revs.
I have not checked the timing chain tension. I have not read anything on the cam chain tensioner yet. - could be a spot of trouble, perhaps?.

Any suggestions on where to start first?
I have read a post or two where this same problem comes up, but there is never a follow up as to what the person found to be the problem.

Oh, and the exhaust is stock on the right side and not so stock on the left. It looks like a big washer was welded on with a small pipe going thru it. I took a flashlight and looked in both the right and left and they both actually look the same on the inside.
Here's a pic of the left and right side.

Thanks in advance!
Todd
 

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It's not the cam chain.

Your advance needs fixing no matter what, do that first.

Check your compression. For real, no fingers over the spark plug holes.

Given good compression and proper ignition your symptoms sound like main jet/metering rod issues, possibly time for a thorough carb cleaning.
 

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You didn't mention it, but I'm sure you sync'd your carbs throttle cable

Is your carb piston sliding freely and not getting hung up?

Your advance unit lubed and springs in good shape?
 

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Discussion Starter · #4 ·
Throttle cables in sync.
Carbs rebuilt by me. Oh crap, float height? I don't think I ever checked that. Great @#$%#@!#$&*$#@ (me cussing) just @#$%^$#@ great. I just remembered that.
Darn, Shoot, Phooey, Crud.

I will check the slide first. Will have to take off air cleaner etc...
Be back in a few.
 
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